Leading Practices to Reduce the Possibility of a Natural Gas Over-Pressurization Event

Transcription

1 Leading Practices to Reduce the Possibility of a Natural Gas Over-Pressurization Event November 26, 2018

2 DISCLAIMER The American Gas Association s (AGA) Operations and Engineering Section provides a forum for industry experts to bring their collective knowledge together to continuously improve in the areas of operating, engineering and technology when producing, gathering, transporting, storing, distributing, measuring and utilizing natural gas. AGA publications such as this provide for the exchange of information within the natural gas industry and scientific, trade and governmental organizations. Many AGA publications are prepared or sponsored by an AGA Operations and Engineering Section technical committee. While AGA may administer the process, neither AGA nor the technical committee independently tests, evaluates or verifies the accuracy of any information or the soundness of any judgments contained therein. AGA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of or reliance on AGA publications. AGA makes no guaranty or warranty as to the accuracy and completeness of any information published therein. The information contained therein is provided on an as is basis and AGA makes no representations or warranties including any expressed or implied warranty of merchantability or fitness for a particular purpose. In issuing and making this document available, AGA is not undertaking to render professional or other services for or on behalf of any person or entity. Nor is AGA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on their own independent judgment or, as appropriate, seek advice of a competent professional in determining the exercise of reasonable care in any given circumstances. AGA has no power, nor does it undertake, to police or enforce compliance with the contents of this document. Nor does AGA list, certify, test or inspect products, designs or installations for compliance with this document. Any certification or other statement of compliance is solely the responsibility of the certifier or maker of the statement. AGA does not take any position with respect to the validity of any patent rights asserted in connection with any items that are mentioned in or are the subject of AGA publications, and AGA disclaims liability for the infringement of any patent resulting from the use of or reliance on its publications. Users of these publications are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Users of this publication should consult applicable federal, state and local laws and regulations. AGA does not, through its publications intend to urge action that is not in compliance with applicable laws, and its publications may not be construed as doing so. Changes to this document may become necessary from time to time. If changes are believed appropriate by any person or entity, such suggested changes should be communicated to AGA in writing and sent to: Operations & Engineering Section, American Gas Association, 400 North Capitol Street, NW, 4 th Floor, Washington, DC 20001, U.S.A. Suggested changes must include: contact information, including name, address and any corporate affiliation; full name of the document; suggested revisions to the text of the document; the rationale for the suggested revisions; and permission to use the suggested revisions in an amended publication of the document. Copyright 2018, American Gas Association, All Rights Reserved 1

3 The purpose of this document is to provide guidance to natural gas utilities on leading practices that may supplement current practices to reduce the possibility of an over-pressurization event, especially in a utilization pressure system. AGA s member companies are steadfastly dedicated to the continued delivery of natural gas in a safe and reliable fashion to the communities they serve. We are committed to sharing leading practices and lessons learned across our industry in order to enhance our collective performance. Many of the leading practices described in this document are currently implemented at natural gas utilities but they are not uniformly applicable to all systems nor exclusive. This document contains practices above and beyond minimum federal regulations. Depending on each system s unique characteristics, it is the consensus of AGA members that appropriate implementation of the practices in this document may reduce the possibility of overpressurization. The determination of whether to adopt any of the items contained in this technical note is individual to each company, recognizing that not all practices will be applicable given the size, configuration, pressures, and other features of a particular system. The need to implement every practice and the timing of any implementation of the practices described in this document will vary with each natural gas utility and the specific environment in which they operate. The actions within this document should be evaluated in light of each operator s system, geographic variables, the operator s independent integrity assessment, risk analysis and mitigation strategy and what has been deemed reasonable and prudent by their state regulators. Therefore, not all of the practices described in this document will be applicable to all operators. As used herein, the term should is not mandatory but is to be acted upon as appropriate. This document is intended to serve as a technical resource for natural gas operators. Note that the appendix is an excerpt from an AGA publication which contains additional background information and practices which address overpressure protection and the related topic of system regulation. Since the scope of this document is limited and primarily focused on practices to further reduce the possibility of an over-pressurization event, it does not identify leading practices in other areas, including emergency response. The reader should not conclude that the AGA members believe these are unimportant issues. 2

4 . Contents Section 1: Design of Distribution Systems and Regulator Stations... 4 Background of Natural Gas Systems... 4 Design Practices For all Pressure Classifications... 6 Additional Design Practices for Utilization Pressure (i.e. low pressure LP ) Systems... 9 Section 2: Operating Procedures and Practices Regular maintenance for regulator stations System Monitoring Records Damage Prevention Construction and Work Permitting Process Tie-ins and Uprates Standard Operations and Maintenance Practices Construction, Tie-Ins, Tapping, Uprates, and Abandonments Practices Damage Prevention Practices Records Practices Section 3: Human Factors Management of Change (MOC) Training for Prevention and Recognition of Abnormal Operating Conditions Operator Qualification Field Oversight Management of Change (MOC) Practices Training for Prevention and Recognition of AOCs Practices Field Oversight Practices Section 4: Managing the Risk of an Over-pressurization Event Distribution Integrity Management Support from stakeholders, communities, and customers General Practices Industry practices specific to DIMP: Glossary

5 Section 1: Design of Distribution Systems and Regulator Stations Background of Natural Gas Systems Natural gas utilities provide service to residential, commercial, and industrial customers. The typical source of the utility s gas supply comes from pipelines that operate at a high pressure. The high elevated pressure allows the gas supply to travel many miles underground throughout the country. For delivery to residential, commercial, and industrial customers, the pressure must be reduced to a lower pressure level that the customer can receive. The gas industry has used pressure regulators to reduce pressure since the 1800s. The primary function of a pressure regulator is to maintain constant, reduced pressure at the outlet. This is accomplished by varying the regulator s position/opening such that the flow of gas through the regulator station matches the demand on the downstream system. As system demand decreases, the flow through the regulator decreases as the regulator responds to the increase in pressure in the system. Conversely, as system demand increases, the regulator flow must also increase (otherwise the system may run out of supply). The types of gas regulators available for selection by the gas industry range in size depending on the system demand being supplied. Despite their diverse sizes, they can be categorized according to application: appliance, service, industrial, and distribution/transmission systems. Just as there are many regulator choices there are also multiple points where regulators are used for pressure reduction. Common design points include city gate stations, district regulator stations, farm taps, industrial customers and residential customers. City gate stations are a primary pressure reduction point for the high-pressure pipelines that transfer gas to distribution systems. The basic function of these stations is to link high-pressure transmission pipelines to distribution pipe systems. A city gate station usually performs three primary functions: 1. It reduces the pipeline pressure to operating pressure of the utility pipe system. 2. It measures the volume of gas delivered to the utility. 3. Odorant is added to the natural gas to enable the detection of gas. District regulator (DR) stations are pressure-reducing facilities downstream of city gate stations that reduce the pressure in the pipeline coming from the city gate to a lower pressure. This lower pressure downstream of a DR is more suitable for providing service to customers or other distribution networks within the LDC s distribution system. The operating pressure of the distribution systems upstream of district regulator stations vary depending on the distribution systems configuration and downstream demands. The pressure of the distribution systems downstream of these DR stations usually vary from about 100 pounds per square inch gauge (psig) to as low as 0.25 psig. These downstream pressures may be categorized as high, medium, or low-pressure distribution networks. Although classification of pipe networks by pressure level is common, terminology and the pressure range covered by each class varies between utility operators and systems. System pressures are affected by a service area s demand with respect 4

6 to customer usage needs, weather considerations, design loads, and other maintenance requirements. High pressure networks offer service to residential customers either directly or by means of a medium or low-pressure distribution networks. Whenever gas is fed from a network operated at a higher pressure to one operated at a lower pressure, a pressure regulator is installed between the two points. A pressure regulator will reduce the higher pressure of incoming gas to lower pressure of outgoing gas. The design criteria for each system are unique, leading to different designs for each regulator station. Some examples of factors that cause variations in regulator station design include: Maximum and minimum flow requirements based on the customers demand Upstream and downstream maximum allowable operating pressure (MAOP) Forecasted future flow requirements Maximum and minimum pressures available from the upstream system Number of stages for pressure reduction Number of supply inputs - fed by single or multiple supply lines Gas temperature and gas quality Location and environmental conditions, driven by local ordinances Amount of land or area available for the station to be built Gas contaminants (such as sulfur, liquids and particulate debris) Proximity to highly populated areas Station design aspects that vary include: Type of regulator(s) or control valves installed Above Ground versus Below Ground The quantity of regulators installed Location of downstream pressure sensing points Type of over-pressure protection installed Use of heaters Equipment to remove contaminants from the gas stream Equipment to allow remote control of pressure settings Use of odorizers Distribution systems are designed to provide safe, efficient, and reliable service to the customer. Customer fuel lines operate at low pressure to ensure proper appliance performance, typically less than 1 psig. A lower pressure system that delivers gas at minimum delivery pressure is sometimes referred to as a utilization pressure system. Consequently, it is not necessary to install a service regulator to reduce pressure for each customer when the system operates at utilization pressure. Operating a system designed for minimum delivery pressure can be challenging as the needs of the system are dynamic and change with demand. Extreme cold weather days, customer 5

7 demand changes, etc. require accurate pressure control. Utilization pressure systems have typically been designed as fully looped systems. Fully looped systems minimized customer outages by providing many alternative paths by which gas could reach the customer. When a distribution system is designed at pressures higher than utilization, i.e., above the customers delivery pressure, service regulators are installed at the customer meter set to reduce and control the pressure to a uniform level to the customer. The modern gas regulator is a highly reliable device; however, failures could potentially occur due to a number of reasons such as physical damage, equipment malfunction, and the presence of foreign material in the gas stream. The industry has developed multiple layers of protection to mitigate the potential of over-pressurization. While there is no design standard that is applicable to all situations, some common over-pressure protection designs include: Use of in-line monitor regulators that control pressure upon failure of the primary control regulator. Use of relief devices that vent excess gas pressure to the atmosphere. Use of automatic-shutoff devices, such as positive shut off valves and fail close regulators to interrupt the supply of gas. Installation of filters and strainers to eliminate debris entering a regulator. Deployment of signaling devices that notify operating personnel of equipment failure or abnormal operating conditions (AOCs). Use of telemetry and transducers that are monitored remotely with corresponding alarm set points. Customers on systems that operate at pressures higher than utilization system pressures have their own individual regulator located at the meter. Customers served from utilization systems do not require individual over-pressure protection because the entire distribution system operating at utilization pressure has over-pressure protection at the district regulator station or at another location. The basics of over-pressure protection requires the design to protect the downstream piping system from excessive pressure. Design Practices For all Pressure Classifications The following practices should be considered when designing new regulator stations, modifying existing stations, or selecting over-pressure protection. System, environmental, and other factors unique to each operator will determine the applicability of each practice: 1. Practice: Include pressure monitoring and alarm functionality within designs of systems and formalize approval via a Management of Change (MOC) process. Description: Design for a mechanism to generate an alarm condition. Mechanisms may include: alarm relief ( whistle, tattle-tale, token ), full relief valves, pressure recording devices, pressure signals to Gas Control, etc. Critical pressure points should be capable of alarming or generating a real time notification (relief, whistle, token alarm to Gas Control or Operations, etc.) when an AOC occurs. Safety sensitive pressure monitoring points should be 6

8 field verified via the communications network to Gas Control. Field equipment should be calibrated and inspected to confirm alarm set points are properly configured to trigger at the appropriate upper and lower limits. Consider any modifications to critical regulators, pressure monitoring points and overpressure devices be validated through a formal MOC process. 2. Practice: Design stations with remotely controlled valves and regulators. Description: When designing new systems consider remotely controlled valves and regulators which may aid in the quick isolation of critical stations, where appropriate. 3. Design for Response Time. Description: When using monitor control valves and slam shut valves, recognize the inherent time to respond/time to close to enable adequate response. Equipment set points and operational characteristics should be taken into consideration. 4. Practice: Size over-pressure equipment to current load and monitor for future load needs. Description: Primary regulators, monitor regulators and relief valves must be sized and designed to enable adequate over-pressure protection. Parameters which dictate proper sizing, such as system demand requirements, must be evaluated. All station equipment must be designed to operate within its intended operating range. Periodically contact industrial customers to verify gas usage to understand if load patterns have changed, or if a significant change to their future load profile is anticipated. In completing this practice, operators should confirm system equipment is sized appropriately to deliver load and gas pressure safely. 5. Practice: Design sensing lines to be protected and located close to or inside the regulator station. Description: Sensing lines should be sized appropriately for the regulator and account for restrictions (i.e., reduced port ball valves, needle valves). Each regulator and relief valve shall have an individual sensing line, per 49 CFR Part 192 regulations. Sensing line taps should be located within the station side of isolation valves, and as close to the station as possible. If underground, route the sensing lines for supply regulators and over pressure protective devices to different locations to minimize the possibility of multiple lines being damaged by an excavation. 6. Practice: Mitigate the possibility that a common mode of failure, or a single event, could take out the primary ( worker ) and the monitor regulators. Description: Single events can impact the primary and backup regulator. Determine what can be done to reduce the possibility that any single event can disrupt both regulators. 7. Practice: Install slam shut valves, where practicable Description: Installing slam shut valves is an option for over-pressure protection and loss of sensing pressure and maybe effective for additional system protection. Slam shut valves may be considered, particularly in systems where multiple regulator stations supply gas to an area. 7

9 8. Practice: Create standard regulator station design templates that are approved by a licensed professional engineer or engineer with equivalent experience and technical knowledge. Description: Establish standard designs for regulator stations. Require that any deviation from the standard should be approved through a design management of change (MOC) process that has been reviewed and approved by a licensed, professional engineer (PE) or engineer with equivalent experience and technical knowledge. 9. Practice: Add or improve remote controls of stations and valves. Description: Consider designing critical systems, including regulator stations, to be monitored and controlled remotely, or by a Gas Control room via a SCADA system. 10. Practice: Design for atmospheric vent lines to be unobstructed for proper venting. Description: In cases where vent lines are designed with below ground regulators, separate lines should be installed for each piece of control equipment and terminate so they are not impacted by water infiltration into the vault. Above ground facilities should be vented to avoid the impact of insects, ice, and environmental forces. Confirm that all vent lines are secured from motion or vibration. 11. Practice: Above ground regulator sets and other critical regulator station equipment should be protected from vehicular and pedestrian damage. Description: Bollards should be properly sized and installed to protect regulators from any potential vehicular traffic. Other considerations for protection include: locked fences around regulator stations, locked bypass valves, weather protection, and added protection for control lines from damage. 12. Practice: Design for station security. Description: Critical station valves should be designed with locking devices, as needed, so they can be locked in their normal operating position. 13. Practice: Design bypass valve configurations for secure operation at stations. Description: Two bypass valves should be considered in series to enable quick control if one valve fails during operation. To prevent unintentional operation, locking mechanisms should be installed on the valves when not in use. Consider locating bypass valves at a distance from operating equipment to confirm safe accessibility and operability in an abnormal operating condition, i.e. Fire Scenarios. 14. Practice: Enhance regulator station design requirements in areas with a history of contaminants in the gas stream. Description: Contaminants can impact pressure regulation equipment operation. Consider installation of a properly sized separator to remove rust, dust, liquids, or debris upstream of the regulator station. Consider installing heaters to reduce potential for freeze-ups and sulfur filters on pilot-operated regulation equipment in areas with known sulfur issues. 8

10 15. Practice: Confirm flow path to relief valves are not compromised. Description: Steps should be taken to not compromise the flow path to a system relief valve during construction (abandonments, new construction, reconfigurations, and renewals). 16. Practice: Emerging technologies are monitored by the industry and should be considered in future over-pressure designs. Description: When technology develops operators should consider, where feasible, to integrate new technologies that may enhance over-pressure protection. Additional Design Practices for Utilization Pressure (i.e. low pressure LP ) Systems In addition to the above, the following practices are options for operators to consider implementing, depending on the uniqueness of their LP system and the local environment. 1. Practice: Design additional over-pressure protection on utilization pressure systems, where feasible. Description: Consider adding additional layer(s) of protection for over-pressure protection. Design could include an operator, monitor, slam shut, full capacity relief valve, or a customer service regulator, where feasible. Consider utilizing relief devices throughout the system, particularly in a utilization pressure system fed exclusively by primary/monitor stations. This is an additional control to mitigate the potential for over-pressuring a system and also acts as an alarm. Urban environments may add additional complexity to finding a suitable location for the relief valve blow down stack. Locations can be at the regulator station or a distance downstream of the station. 2. Practice: Design for new or replacement low pressure and utilization pressure district regulator stations to include pressure monitoring. Description: Where practical, design the system so there is pressure monitoring of all utilization pressure stations and systems. 9

11 Section 2: Operating Procedures and Practices This section includes guidance on Operational Procedures, Practices, and Standards that enhance the reliability and safety of natural gas systems affecting System Regulation, Regulator Station Design, and Overpressure Protection. It is the operator s responsibility to implement procedures and practices such that its natural gas systems are operated and maintained in a safe manner. Such practices may include, but are not limited to, the items in this section. Regular maintenance for regulator stations Regular inspections and maintenance activities can help determine that equipment in pressure reduction stations is working properly. The frequency of station inspections over and above regulatory requirements should be based on the following: The type of station (e.g., City Gate, District, Customer Sales, etc.) The type of equipment at the regulator station (i.e. remote monitoring) The configuration and number of the regulator runs at the station The style of regulators used (e.g., self-operated, spring-loaded, boot-style, pilot-loaded, pilot-unloaded) Whether the regulator is above or below-grade Historical performance of a particular regulator or station Gas quality System or sub-system throughput The amount of pressure cut, or differential, across the regulator station Some of the regular maintenance activities performed on a station may include: Visual inspection of the station to identify risks and/or concerns that may have arisen since the last inspection Equipment functional inspections and calibrations Regulator operational inspections (visual inspection, check for regulator lock-up) Regulator maintenance inspections (regulator tear-down, inspection, cleaning, replacement of soft goods, filter inspection or replacement) Annual leak survey SCADA field electronic sensing equipment point-to-point verifications System Monitoring Strategically placed telemetry equipment monitors key parameters to assist with maintaining safe and reliable service. Telemetry systems include measuring instruments or detectors, a medium to transmit data, a receiver, and a system that records/displays data. If system control equipment is in place, an operator s Gas Control group monitors the data received, and either acts upon any alarms by making remote adjustments, or dispatches field personnel to investigate issues. Stand-alone electronic pressure recorders can also alert of an overpressure or underpressure situation. If an operator has a SCADA system in place, these recorders can be programmed to send an alarm to Gas Control whenever system pressures fall outside acceptable levels. Operations personnel can be dispatched to investigate the problem. 10

12 Records Complete records and drawings should be retained and documented on any work related to gas regulation or overpressure equipment, in accordance with the operator s records retention policy. This includes the location of all taps, control lines, and vent lines. As practical, records and drawings should include accurate dimensions and notations of as-installed conditions. Operators should consider having a system in place to make this information readily available to any field personnel who may need it, such as locating technicians. Mapping of all gas systems enables proper planning of system upgrade activities and maintenance. System interconnection points, pressure reduction stations and valves should be included in records. Damage Prevention Operators should work with their local One Call Center(s) to screen dig tickets that are in the vicinity of system gas regulation or overpressure equipment. Locates performed near system gas regulation or overpressure equipment should include marking the location of all taps, control lines, and vent lines. In addition, operators should consider monitoring excavation activity in the immediate vicinity of buried control lines and take necessary actions to protect them from damage. Construction and Work Permitting Process Operators should put in place processes and job-specific procedures for any planned work that could result in a significant interruption of gas flow to the network, require significant internal/external resource coordination activities, and/or involve multiple coordinated procedures. Procedures should identify all stakeholders when work is done on gas regulation or overpressure equipment that could cause adverse effects. Tie-ins and Uprates Tie in connections between two segments of natural gas piping typically take place between an existing pipeline and a newly installed pipeline, and often as part of Replacement/ Modernization Programs. During any tie-in procedure, pipeline pressures on both sides of the tie-in point should be monitored to: Maintain the pressure in the pipelines where the flow of gas is stopped; Prevent connecting mains with different operating pressures and MAOPs; and Verify that mains being connected are the ones intended to be connected to (not abandoned or operating at a different pressure) Additional precautions should be taken when any work is done on or near system regulators and overpressure equipment. Field personnel should have a clear understanding of the impact that their work could have on a gas system, especially when working on utilization pressure systems where customers do not have secondary pressure regulation. Tie-ins and uprates should be done in a controlled manner where all departments, including Gas Control, are communicating as work is being performed. Decision points (go/no go) in the procedure should be identified and clearly communicated prior to initiating the pressure increase. 11

13 Standard Operations and Maintenance Practices 1. Practice: Create and follow written procedures. Description: Written procedures aid in successful execution of tasks and processes in projects. Common procedures should be standardized and included in the Operations Manual. Written procedures should be present or accessible from the job site. Complex work should be reviewed before being issued to the field, by all departments involved in the project. For example, when applicable, Engineering, Operations (contractors when appropriate), and Gas Control should review the procedures. In complex projects, a checklist can function as a written procedure. A process for approving field changes to a procedure should be specified. Operators should consider requiring review and approval of complex procedures by a licensed professional engineer (PE) or engineer with equivalent experience and technical knowledge. Procedures should contain the necessary steps in proper order to be completed prior to beginning field work (such as verification of accessibility of valves and their position, below ground fittings, all isolation points, and operating conditions of the system, etc.). System designations and operating pressures should be in the procedures to ensure recognition of over or under pressure event. Restrictions or AOC s that alter a procedure (weather, generation load, etc.) should be accounted for and a process for approving field changes should be specified. Refer to section (D) of this section for records retention. 2. Practice: Use appropriate personnel and equipment to monitor pressures during work. Description: Use calibrated gauges, of the type and pressure range suitable for the system being worked on and continuously observe in appropriate locations to monitor the operating pressures of the system during any activity that could potentially cause over-pressurization. Leave gauges on for an appropriate length of time after the work is completed, to identify any lagging pressure changes. Consider the use of qualified pressure control personnel to monitor the operation of regulator stations within the scope of work. 3. Practice: Consider eliminating direct connections between systems operating at different pressures. Description: If this configuration is part of emergency pressure support of a system, the valves should be labeled, locked out/tagged out, and clearly identified on all maps. Consider adding gauge connections on both sides of these valves. Prevent operating a valve that connects a higher pressure system to a lower pressure system, especially a utilization pressure system. 4. Practice: Lock and tag all bypass valves. Description: Regulator station bypass valves should be locked and tagged to prevent unintended or unauthorized operation resulting in an AOC. Provide security around bypass valves if unlocked. Consider a special valve key or valve cover preventing anyone other than qualified staff from operating a regulator station bypass valve. The need for locking devices should be balanced with the weather and environmental conditions of the area and the 12

14 impact on emergency response. Consider implementing a formal Lock-out Tag-out (LOTO) program to expressly spell out when LOTO is required and how it protects the operator from overpressure events. 5. Practice: Exercise critical valves prior to initiating a procedure. Description: Operations personnel should confirm location of all valves that are critical to isolation of a work area or a pre-determined valve isolation plan. Operator should exercise critical valves to verify that they are operable. Confirm that the critical valves can be operated, while monitoring system pressures on both sides of the critical valve. See Practice 2 above regarding pressure monitoring and use of gauges while operating valves. 6. Practice: Written procedures should include AOCs. Description: The expected range of pressures during the procedure, as well as the MAOP of the system should be communicated to personnel in the field and control room, if the utility has a gas control. Actions to take in response to abnormal pressures should also be communicated. Field personnel should verify the pressure and/or flows measured in the field are the same as what the Gas System Controller is observing in the control room, when applicable. Emergency contact information for gas company personnel and emergency first responders should be available/accessible to everyone on the job site. 7. Practice: Develop a standard written procedure for notifying emergency first responders and provide clear instructions on relief devices. Description: Both Dispatch and Gas Control operators should use the same set procedure to notify emergency first responder personnel when there is an AOC. If the notification is to inform first responders that a relief valve is blowing, the caller should also inform them that the equipment is operating as designed, and that the relief device should be allowed to continue relieving pressure. 8. Practice: Pre-job briefing (tailboard meeting) to review procedure before beginning. Description: A briefing with Operations personnel performing the work should be held. Updates to the job briefing should occur based on changing conditions (weather changes, shift changes for employees, transitioning between day shift and night shift, significant delays between start and finish of procedure, etc.) Identify scope of work involved and involve Gas Control, if applicable, when the procedure will result in a significant change in system pressures or when over-pressurization is a threat. Verify SCADA equipment that is being used as flow/pressure monitoring is properly communicating to control room on the day of work being performed. 9. Practice: Data refresh rate awareness and timeliness. Description: During standard operations or procedures, Gas Control should be aware of how often SCADA sites are polled, and adjust responses accordingly. When possible, consider increasing frequency of polling on systems where active work is being performed on facilities considered to be critical, to set an appropriate time between readings. 13

15 10. Practice: Planned maintenance work should be communicated to Gas Control. Description: For systems that have a Gas Control, consider establishing communication protocols based on the significance and potential impact the maintenance work may have on field and control room operations. 11. Practice: Maintain awareness of activities in the upstream system to confirm system changes or work performed has not compromised pressure regulation equipment. Description: Operators should consider a means to minimize the potential for fluid and debris to enter the gas stream and perform inspections after work is performed upstream of a regulator station, as needed, to mitigate the potential impact of any debris or liquids that entered the regulator station. For example, transmission in-line inspections may dislodge scale and debris which could travel downstream into regulator stations. Construction, Tie-Ins, Tapping, Uprates, and Abandonments Practices 1. Practice: All regulator control lines and service lines to structures in the area of excavation work should be located. Description: The written procedure and the locate markings should indicate if the lines are connected to the main being worked on. Structures at street intersections and main crossings are particularly vulnerable. Pressure regulator control lines within the excavation area should be exposed by hand or with soft-dig excavation equipment and protected during excavation. Facilities that were incorrectly mapped or unmapped should be documented and communicated to the appropriate group to be added to the map or corrected. 2. Practice: Prior to an uprate operation, evaluate the location and placement of any pressure regulator equipment, control lines, and relief valves in regards to the uprate strategy/plan. Description: An uprate procedure is a detailed process to change the MAOP of a system to a higher pressure based on system design, construction and pressure test. The procedure should include a review of the existing regulator stations to determine if their locations are acceptable and the installation meets system demands and company standards. A review of the operating history of the regulator station should also be conducted, where applicable. The results of the review and any changes, modifications or new installations should be included in the procedure and appropriately sequenced. Operators should require review and approval of system uprates by a licensed professional engineer (PE) or engineer with equivalent experience and technical knowledge. 3. Practice: Simplify complex procedures by breaking into multiple, less complex procedures. Description: Considerations should be included during project planning to maintain manageable scope of work activities and procedures. Complex projects with numerous tieins or other involved work activities could be broken into multiple manageable procedures to reduce risk of unforeseen abnormal conditions. 14

16 4. Practice: Work-in-Progress and Work-in-Planning notations ( clouds ) on maps. Description: Construction planners should identify and notify all affected departments of planned construction activity. A drawing should be provided to visually identify all impacted work areas across multiple departments or service areas. This can prevent separate groups from performing work on the same, or related systems and creating operational issues. Damage Prevention Practices A serious threat to the integrity of a natural gas facility is the possible damage resulting from excavation, external forces, or pedestrians around piping and regulator stations. Damage to the piping near a regulator or the control lines of a regulator can cause an AOC (abnormal operating conditions), sending high pressure gas downstream. Below are some of the practices in which the threat of such damage may be mitigated. 1. Practice: Establish buffer around the regulator station for One Call tickets. Description: All one call tickets should be reviewed to determine location and prioritized if near a regulator station. Consider a set perimeter for prioritization such as within X feet of a station. Extra precaution should be taken in these areas, and procedures should be developed to reflect the extra actions to be taken by inspectors, personnel observing 2 nd and 3 rd party excavations, field operations personnel, etc. The benefits of technology, such as GIS, should be considered to recognize these buffer zones, potentially automating the prioritization of one call tickets 2. Practice: Have operator personnel on site observing 2 nd or 3 rd party excavation activities in close proximity to regulator stations or mains with buried control lines. Description: Operators should consider having qualified personnel monitoring construction within the specified buffer zone around regulator stations with buried control lines. This provides trained response to abnormal conditions that may occur during the work, including stop work authority. This person should conduct pre-construction meeting with the 2nd or 3rd-party construction crew prior to any work being performed to explain the importance of avoiding any damage. The excavator should hand dig or use another form of soft digging technology when digging around a regulator station. Consider shutting-in stations, when possible, or putting them on local control. 3. Practice: When working in the vicinity of regulator stations and utilization pressure systems, create a process to identify potential AOCs. Description: Operator should provide field personnel with a standardized checklist that covers threats that could cause an AOC. Confirm the checklist is used prior to performing work. 4. Practice: Locate and maintain marks for buried control (sensing) lines. Description: Locate and mark all buried control lines and associated piping. Hand dig or use soft dig technology to excavate around control lines. Consider installing above ground signage, below grade protection plates and/or marker balls to indicate buried gas utility piping below to increase awareness. 15

17 5. Practice: Protection of control lines at regulator stations. Description: Measures to protect control lines include installing with hard pipe or heavy wall stainless steel tubing, or locking or securing by some other means such as taking off valve handles, and eliminating the ability to shut a control line valve without a wrench. Records Practices Records are critical for operations, maintenance, risk identification, and analysis. Operators should have a documented process for creation, collection, identification, distribution, and storage of records. The process should identify authority and responsibility for managing records. 1. Practice: Use maps and records on site to complete work Description: Utilize appropriate maps, records, and construction drawings to complete work as designed. Perform a mapping system review in coordination with the applicable personnel, such as representatives from engineering, pressure control, and gas control, when applicable, to validate and update that control line and pressure sensor locations are shown in the mapping system as needed. Utilize records and maps of all interconnects and regulator stations feeding into a given system. Regulator Station drawings should be field verified for control line locations and be available to company personnel onsite at the station. If station operation is part of the procedure, a drawing of the station should also be a part of the work package. Control point locations should be accurate and updated during any field working procedure. Verify accessible valves and their position (normally open are open, etc.), below ground fittings, and operating conditions of the system should be performed as needed. All gas supply interconnects and location of company owned facilities need to be mapped or in written form. 2. Practice: Implement a Records Management System Description: Records management systems can track equipment in the system, as well as maintenance records of the equipment. Consider a system that can notify the responsible parties in advance of maintenance schedules for pending work. 3. Practice: Management of separation valves. Description: Valves that separate systems operating at different pressures should be eliminated, where possible, as noted under Standard Operations and Maintenance Practices, Practice 3. If it is not possible to eliminate separation valves, they should be clearly indicated both on system maps and in the field. This practice is not applicable for station bypass valves. 4. Practice: Labels for critical valves should indicate the direction to open/close and number of turns to full open or full closed. Description: Asset labeling in the field should include not only the critical valve number as shown in the record management system and on maps and station drawings, but also indicate which direction the handle or wheel should be turned to open and close the critical valve, 16

18 and the number of turns to move the critical valve from full open to full closed. Alternatively, this information may be provided to field personnel via electronic devices. 5. Practice: Collect and maintain precise location data for equipment, sensors, critical valves, and control lines, where possible. Description: When field personnel are performing maintenance on equipment in the field, consider taking GPS readings or precise measurements. Include in records for all pressure sensors, regulators, critical valves, and control lines. 6. Practice: Complete and retain the as-built drawing for the installation or reconfigurations of pressure regulation assets in a timely fashion. Description: Upon completion of pressure regulation asset installations or reconfigurations, field mark-ups should be verified and updated into a records system for all assets related to pressure regulation. 17

19 Section 3: Human Factors Understanding and addressing human factors is critical to reducing the frequency and severity of pipeline incidents caused by over-pressurization. Considerations include: Promote a positive pipeline safety culture, which influences the attitudes of employees and contractors regarding pipeline safety and drives a conscious effort to reduce the risk of overpressurization. Identify and communicate to all personnel safety-critical tasks for each project and system operation tasks that may result in over-pressurization if procedures are not followed. Encourage use of error prevention tools such as 3-way communication. Identify all personnel performing the task are qualified for the task. Identify AOCs and the appropriate actions to be taken should they occur by involving construction, operations, gas/pressure control, and design personnel. Identify where human failures have a high likelihood of occurring during each step of a task and determine measures to prevent or mitigate the likelihood of over-pressurization occurrence. Wherever possible, design the system to account for the possibility of human failure as discussed in Sections 1 & 2, minimizing the potential for human error in the operation or maintenance of the system. Management of Change (MOC) MOC process is a leading practice for evaluating and mitigating the risk of significant changes to a pipeline system. Operators should consider developing a MOC process for all plans that have a potential for over-pressurization. The process should communicate the level of authority required to make changes to the design and/or written project plan. For example, inspectors and/or operator personnel may have authority to make certain types of field changes, while more complex changes may have to be approved by a licensed PE or engineer with equivalent experience and technical knowledge. Training for Prevention and Recognition of Abnormal Operating Conditions The training of operator and contractor personnel for executing construction, operation, and maintenance activities is essential. Personnel should be well-trained to perform their assigned duties. Prior to the start of construction, the operator must determine the knowledge level and skill set required to perform covered tasks. It is the responsibility of the operator to verify that personnel are qualified and have the knowledge skills and ability to perform each task assigned to them. Each employee or contractor must demonstrate a fundamental knowledge of performing the task including recognizing AOCs involving over-pressurization of a system along with possessing the technical and operational experience required to perform the work safely. Due to the unique operating characteristics of a utilization pressure system, gas utility, contractor, and inspector personnel should have additional training on the different operating characteristics of a utilization pressure system. Gas utility and contractor personnel must be trained on how to recognize AOCs and what responses are required to mitigate or minimize their impact. AOCs associated with operating a utilization pressure system should be identified and 18

20 operational actions defined to address these AOCs. In addition, design and gas control personnel should consider specific training on the operating characteristics of a utilization pressure system and the importance of ensuring the accuracy of the plans and documentation of all proposed work such as tie-ins, abandonments, critical operating valves, regulator stations, regulator station sensing lines, location and adequacy of over pressure equipment, uprating procedures, proper operation of SCADA system, response to SCADA alarms, and the identification of AOCs. When necessary, design personnel should make field visits to determine the accuracy of maps, as built documentation, location of critical infrastructures including regulator sensing lines, and SCADA locations as part of the project design. Designing a safe, reliable, and efficient gas delivery system requires system knowledge and expertise. Some gas utilities require a licensed PE or engineer with equivalent experience and technical knowledge to design regulator stations and over-pressure equipment. Operator Qualification (OQ) An essential part of the work planning process is the identification of all covered tasks prior to the project commencing. Only qualified individuals or a person under the direct span of control of a qualified individual (when allowed) can be assigned a covered task. As part of the work plan, the covered tasks should be identified for each step of the process and incorporated into the work plan. During the construction phase, the inspector(s) or company representative(s) must be fully aware of the operator qualifications of all individuals including those who are performing a task without supervision and those who will be required to perform tasks under direct line of sight observation of another qualified individual. Anytime there is a change in personnel on the construction crew, or the procedures change, the operator qualifications should be re-verified. Field Oversight Field oversight including inspection, quality control and quality assurance measures of qualified personnel should be considered throughout construction, maintenance and operations processes. The level of inspection is specified by company policy and includes additional provisions for more complex projects and/or work tasks. It is the operator s responsibility to provide documented procedures for qualified personnel detailing the step by step guide that directs them through a pressure system control work task. Field oversight activities can help with the understanding and execution of documented procedures during natural gas construction and operations, especially when the work sequence of events is extremely important and adherence to the documented procedure is critical to prevent over-pressurization of the system. For instance, field oversight can prevent a critical step or steps from being missed or not performed in the correct sequence, avoiding an abnormal operating event that could adversely affect the safety of the system. 19